Poor is a very negative condition, Usually the stores will either:
1. Refuse to buy it off you,
2. Pay Very Little Price,
If your in poor condition, Better luck next time! You'll have to find a rare person that still might not even wan't to buy your card. Sorry, But maybe you need some card sleeves.

Good:

The card is in a not good, but okay condition. Sometimes buyers will buy or refuse, It's hard to say. Again you should keep your useful/rich cards in a sleeve or binder.

Fine:

Your in a better condition than great, Still not the best but is a 50% chance they might take it off your hand. Usually prices decrease by not even 75 cents in the "fine" condition.

Near Mint:

You have a very high chance of getting someone or a shop to buy your card. The chances are 75% they will likely buy your card. If they do not, Than it could be a matter of fact that the store is just stupid, Or possibly are greedy and want it in mint.

Mint:

Mint. The best condition you could possibly get. The chances are of them to buy your card is a whopping 99% chance to buy your card! If you have a mint card, Than you are lucky. Most people do not have card sleeves or binders to keep their cards in. Therefore you get the sleeves and you are lucky! Near mint is very close to mint but if you look at it closely, It's not very much the same.

If you have any questions regarding info on this post or any other card condition questions, Feel free to ask me!